First Insights into the Biochemistry of Tube Foot Adhesive from the Sea Urchin Paracentrotus lividus (Echinoidea, Echinodermata)

Abstract

Sea urchins are common inhabitants of wave-swept shores. To withstand the action of waves, they rely on highly specialized independent adhesive organs, the adoral tube feet. The latter are extremely well-designed for temporary adhesion being composed by two functional subunits: (1) an apical disc that produces an adhesive secretion to fasten the sea urchin to the substratum, as well as a deadhesive secretion to allow the animal to move and (2) a stem that bears the tensions placed on the animal by hydrodynamism. Despite their technological potential for the development of new biomimetic underwater adhesives, very little is known about the biochemical composition of sea urchin adhesives. A characterization of sea urchin adhesives is presented using footprints. The latter contain inorganic residues (45.5%), proteins (6.4%), neutral sugars (1.2%), and lipids (2.5%). Moreover, the amino acid composition of the soluble protein fraction revealed a bias toward six amino acids: glycine, alanine, valine, serine, threonine, and asparagine/aspartic acid, which comprise 56.8% of the total residues. In addition, it also presents higher levels of proline (6.8%) and half-cystine (2.6%) than average eukaryotic proteins. Footprint insolubility was partially overcome using strong denaturing and reducing buffers, enabling the visualization of 13 proteins by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The conjugation of mass spectrometry with homology-database search allowed the identification of six proteins: alpha and beta tubulin, actin, and histones H2B, H3, H2A, and H4, whose location and function in the adhesive are discussed but require further investigation. For the remaining unidentified proteins, five de novo-generated peptide sequences were found that were not present in the available protein databases, suggesting that they might be novel or modified proteins.

Serine Protease-mediated Host Invasion by the Parasitic Nematode Steinernema carpocapsae

“…The peptide mixture was purified and concentrated by R2 pore microcolumns (32) and eluted directly to the MALDI plate with 0.5 l of matrix ␣-cyano-4-hydroxycinnamic acid (5 mg/ l in 50% acetonitrile, 5% formic acid). The m/z spectra were acquired in a 4700 Proteomics Analyzer MALDI-TOF/TOF (Applied Biosystems) in both MS and MS/MS mode (33). Protein identification was achieved using a MASCOT search of the UniProtKB data base (downloaded 07/07/2009).…”

Tandem Mass Spectrometry of Peptides

“…The determined amino acid sequences can be used for further functional analysis by homology search of protein sequence databases using adequate programs, namely BLAST-related algorithms (Gaeta, 1998), as "bait for gene fishing" or as a probe for antibody production. The above-described workflow (MS and MS/MS spectra acquisition, de novo sequencing and Blast search) was used for the identification of proteins present in sea urchin (Paracentrotus lividus) tube foot adhesive (Santos et al, 2009). Beside the six proteins identified by homology-database search, other MALDI-MS/MS spectra did not allowed direct protein identification and were further used to automatically generate de novo sequences in an attempt to obtain more information on these proteins.…”

“…Due to this particularity, peptide tandem MS can be used in several applications involving protein characterization and identification, such as the study of proteomes (Franco et al, 2011a,b) and differential proteomics (Puerto et al, 2011) of different organs, tissues, cells or biological fluids. In our laboratory we have also been using this approach for the characterization of proteins with specific function in adhesives (Santos et al, 2009), the identification of protein adducts as potential biomarkers of toxicity (Antunes et al, 2010), and protein glycation (Gomes et al, 2008), it has also been useful in the identification of peptides with immunomodulation properties (Koči et al, 2010). Two types of information obtained by mass spectrometry experiments are used for the study of proteins and peptides.…”

Echinoderm Research 2010

“…When a repellent becomes an attractant: harmful saponins are kairomones that maintain the symbiosis between the Arlequin crab and their sea cucumber hosts [oral presentation] Guillaume Caulier 1 , Patrick Flammang 1 , Pascal Gerbaux 2 , Pricilla Rakotoarisoa 3 & Igor Eeckhaut 1 Arlequin crabs (Lissocarcinus orbicularis) are symbionts found exclusively on the integument or in the buccal/cloacal cavity of several species of sea cucumbers. The population of these crabs was investigated on holothuroids of the barrier reef of Toliara (south-west of Madagascar) from December 2006 to December 2007.…”

“…Calcification is one of the primary targets for studies of the impact of CO 2 -driven climate change in the oceans, and one of the key marine groups most likely to be impacted by predicted climate change events are the echinoderms. Rates of changes are increasingly fast and there is an urgent need to determine the rules that will decide what species will suffer ('losers') or benefit ('winners') from this stressor that can radically alter ecosystem structure (1,2) . We will review the literature and summarize our data collected at the interface between genomics, physiology and ecology.…”